1. Field of the Invention
The present invention relates to a lens barrel that houses a zoom lens or any other lens, and particularly to a lens barrel with a light-blocking plate that prevents flare and ghost images in the lens barrel.
2. Description of the Related Art
To prevent flare and ghost images resulting from unwanted light having entered a barrel, a lens barrel with a light-blocking plate that moves in the barrel as a zoom lens moves has been used. A lens barrel of this type includes a movable lens group and a movable light-blocking plate that move in the optical axis direction, and prevents flare and ghost images from being produced by moving the movable light-blocking plate to a predetermined position according to the position to which the movable lens group has moved (JP-A-06-201966 and JP-A-09-33781, for example).
Another example of the lens barrel that has been proposed includes a movable light-blocking plate having a variable-diameter opening and can prevent flare and ghost images from being produced when a movable lens group moves between a wide-angle position and a telescopic position by adjusting the diameter of the opening in the light-blocking plate while changing the position of the light-blocking plate relative to the movable lens group (JP-A-04-133011 and JP-A-07-294814, for example).
In general, a movable light-blocking plate of this type, in which the diameter of the opening can be changed, is configured in the lens barrel to have a plurality of light-blocking blades supported in such a way that they partially overlaps with each other and can pivot in the direction perpendicular to the optical axis direction. An operation mechanism for pivoting the plurality of light-blocking blades is formed in the lens barrel, and is driven manually by a user or automatically by a microcomputer or any other suitable component disposed in an imaging apparatus or the lens barrel.
Consider now a configuration in which the diameter of the opening in the movable light-blocking plate is automatically changed. When the operation mechanism and a drive source that provides a driving force to the operation mechanism are incorporated in the lens barrel, the lens barrel increases in size and weight. When the lens barrel increases in size and weight, the balance of the image apparatus as a whole deteriorates, and the portability of the lens barrel used as an interchangeable lens is impaired. The operation mechanism and the drive source are therefore desirably provided in a camera body to achieve a compact, lightweight lens barrel.
On the other hand, to change the diameter of the opening formed by the light-blocking blades from the camera body side, an operation member for pivoting the light-blocking blades should extend into the lens barrel, and the light-blocking blades may not be disposed in the region where the operation member pivots, possibly resulting in insufficient blockage of unwanted light.